1) If you just started learning Japanese, I would recommend that you learn Hiragana and/or Katakana first. Because Japanese language has it's own peculiar sound just like all other languages. Reading or writing with alphabet can't really help you learn the exact sound.

2) When you speak Japanese, let your voice resonate at the very front part of your mouth. Chest resonance is not required to sound like a typical native speaker.

3) Each character has the same length. This is very important. For example, こんにちは. Say it like, da da da da da evenly. If you can read music, say it as if the word is made of 5 quarter notes. The small “っ" has the same length too. （いっぴき、わかった、にっぽん “da da da da”）

4) Try not to put any stress on any character (you know I'm not talking about mental stress lol), especially in the beginning of learning. We might put some stress when we want to emphasize something, but basically Japanese words are pronounced with no stress. They just contain differences in pitch.

5) ら行. We pronounce らりるれろalmost the same way as Americans pronounce unstressed version of "t" (e.g. water, quarter, thirty,etc.). In other words, it's just a softer version of the stressed D sound.

6) ふ. Its consonant is different from English “F”. ふ is kind of similar to "who", but there are some differences. When you say "who", you feel the airflow in the middle of your mouth, and let go of the air as you pronounce the vowel. But when you say ふ, you feel the air at the very front part of your mouth, and you have to stop the airflow.

7) Basic tongue positioning is very different from English one. When you speak English, for example “eye”, the root of your tongue is down and relaxed completely, and you pronounce the word with one strong stroke of airflow from the back of your throat. But when you say あい in Japanese, the root of your tongue is raised a bit narrowing the inside mouth, and not relaxed. And it's pronounced as if 2 different sound あ and い are put together.

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Some words are often pronounced differently from their spelling. （e.g. 先生せんせい→ sensei and senseh. Latter one is more colloquial.) In that case, I record the colloquial one.
ガギグゲゴ are basically pronounced nasally when they appear in the second syllable or later. ( For it's been considered to be smooth and neat. But pronouncing without nasal tone is not wrong at all. In fact, most people including me often pronounce it without nasal tone in daily conversations.)